1. Field of the Invention
The present invention relates to a cleaning apparatus and an image forming apparatus.
2. Description of Related Art
In a color image forming apparatus, toner images of each color of YMCK are transferred onto a transfer belt (primary transfer) and the images are further transferred from the transfer belt to the paper (secondary transfer).
After the toner image is transferred onto the paper, residual toner which is not transferred in the secondary transfer remains on the transfer belt. In order to remove the residual toner, a cleaning apparatus is provided in a downstream side of the rotating direction of the transfer belt from the position of secondary transfer.
Generally, the cleaning apparatus is composed including a blade, a brush, a roller, etc. and these are used to remove the residual toner on the transfer belt. Especially, the blade is lately noted as an important component because the blade directly and physically peels off the residual toner on the transfer belt. As for the structure of the blade or surroundings of the blade, there are the following conventional techniques.
Japanese Patent Application Laid-Open Publication No. 2001-42724 discloses a cleaning apparatus where toner is always deposited (accumulated) in a certain area near a contacting section where a blade and transfer belt is in contact with each other and frictional force between the blade and the transfer belt is reduced due to the accumulated toner.
When the frictional force between the blade and the transfer belt is large, the wearing of the blade or the transfer belt is drastic, and these components need to be exchanged in a short period of time. Also, there is a possibility of the blade turning and filming (residual toner which is not wiped) and the image quality drastically decreases.
Japanese Patent Application Laid-Open Publication No. 2004-78113 discloses a cleaning apparatus where the blade accumulates a portion of the removed toner in an accumulating section and the accumulated toner is supplied to the transfer belt to prevent turn of the blade.
Japanese Patent Application Laid-Open Publication No. 2004-109837 discloses a cleaning apparatus where the movement of the toner removed by the blade is controlled by a controlling member and the toner is always in contact with the transfer belt to prevent turn of the blade.
Japanese Patent Application Laid-Open Publication No. 2005-249915 discloses a cleaning apparatus where the toner removed by the blade is accumulated in a space formed by a toner guide member or toner discharging control member and the toner is always supplied to the pressured section between the blade and the transfer belt to prevent turn of the blade.
According to the above conventional cleaning apparatus, all of these include a structure where residual toner is accumulated in the upstream side of the rotating direction of the transfer belt than the blade. The accumulated toner spreads on the rotating transfer belt and a lubricant agent can be supplied to the transfer belt through the toner. When the lubricant agent is supplied on the transfer belt, the wearing of the blade or the transfer belt is reduced. Also, the filming on the transfer belt and the turn of the blade do not occur easily.
However, there is a case where the accumulated toner does not spread on the transfer belt due to the provided position in the image forming apparatus or the amount of the residual toner.
Here, the configuration around the blade of the cleaning apparatus is described with reference to FIG. 8A and FIG. 9A. Also, graphs showing a relation between toner amount and contact width, and a relation between the toner amount and toner pressure is described with reference to FIG. 8B and FIG. 9B.
As shown in FIG. 8A and FIG. 9A, the surrounding of the blade is composed of a blade 11, a roller 12, a scraper 13, a transfer belt B1, etc.
Also, an accumulating section S1 to accumulate toner is formed in the upstream side of the rotating direction of the transfer belt B1 than the blade 11, between the blade 11 and the roller 12.
In FIG. 8A, the accumulating section S1 is formed in a position where the transfer belt B1 is in a vertical direction.
With reference to FIG. 8B, as the accumulated toner amount increases, the contact width where the toner and the transfer belt B1 is in contact increases. When the contact width is increased, sufficient amount of the lubricant agent can be supplied to the transfer belt B1. On the other hand, when the accumulated toner amount increases too much, the toner pressure on the blade 11 becomes large and trouble in the cleaning occurs. Due to the above, the appropriate range of the accumulated toner amount is the allowable width W1 shown in FIG. 8B.
In FIG. 9A, the accumulating section S1 is formed in a position where the transfer belt B1 is tilted 45° from the vertical direction. As shown in FIG. 9A, the advantage of providing the blade 11, the roller 12, etc. (the cleaning apparatus) in a position where the transfer belt B1 is tilted 45° is that the image forming apparatus can be made smaller.
With reference to FIG. 9B, until the accumulated toner amount is a certain amount or more, the contact width in contact with the transfer belt B1 is close to 0. In other words, until the accumulated toner amount is a certain amount or more, as shown in FIG. 9A, the accumulating section S1 does not spread to the transfer belt B1, and the lubricant agent is not supplied to the transfer belt B1. On the other hand, as the sliding increases, the accumulated toner amount is increased, and when the accumulated toner increases too much, the toner pressure on the blade 11 becomes large and the trouble in the cleaning occurs. Due to the above, the appropriate range of the accumulated toner amount is small and the appropriate range is the allowable width W2 shown in FIG. 9B.
The allowable width W1 shown in FIG. 8B compared to the allowable width W2 shown in FIG. 9B can be represented as “allowable width W1>allowable width W2”. Therefore, due to a problem of the configuration of the machine (for example, in order to make the image forming apparatus smaller), when the cleaning apparatus of the conventional configuration is placed as is in a position as shown in FIG. 9A, there is a problem that the allowable width W2 becomes extremely small. When the allowable width W2 is small, the lubricant agent cannot be stably supplied to the transfer belt and problems such as wearing of the blade or the transfer belt, decrease of image quality due to blade turning or filming, etc. occur.